FIG. 12 is a cross-sectional view schematically showing a conventional plasma CVD device. FIG. 13 is a partially enlarged cross-sectional view of the plasma CVD device shown in FIG. 12. The plasma CVD device is a device which deposits a thin film on both surfaces of a substrate to be deposited 101, and although the plasma CVD device is formed bilaterally symmetrically with respect to the substrate to be deposited 101, only the left-hand side is shown in FIG. 12.
The plasma CVD device includes a chamber 102, and the chamber 102 is electrically connected to a ground (not shown). A filament-shaped cathode electrode 103 made of, for example, tantalum is formed within the chamber 102. Both ends of the cathode electrode 103 are electrically connected to a cathode power source 105, and the cathode power source 105 is electrically connected to the ground 106. A funnel-shaped anode 104 is arranged so as to surround a periphery of the cathode electrode 103. The anode 104 has an electrode surface 104a on its front surface.
The substrate to be deposited 101 is arranged within the chamber 102, and the substrate to be deposited 101 is arranged so as to face the cathode electrode 103 and the electrode surface 104a of the anode 104. The substrate to be deposited 101 is electrically connected to the negative potential side of a bias power source (DC power source) 112 serving as an ion acceleration power source, and the positive potential side of the DC power source 112 is electrically connected to the ground 106.
A plasma wall 108 is arranged within the chamber 102 so as to cover a space between each of the cathode electrode 103 and the anode 104 and the substrate to be deposited 101. A cylindrical anti-adhesion member 91 is arranged between each of the plasma wall 108 and the anode 104 and the inner surface of the chamber 102, and the anti-adhesion member 91 is in contact with the inner surface of the chamber 102.
A pedestal 92 is arranged between the anti-adhesion member 91 and the anode 104 and between the back surface of the anode 104 and the inner surface of the chamber 102, and the pedestal 92 is electrically connected to the anode 104. The pedestal 92 is electrically connected to the positive potential side of a DC (direct-current) power source 107, and the negative potential side of the DC power source 107 is electrically connected to the ground 106. Accordingly, the DC power source 107 is electrically connected to the anode 104 via the pedestal 92.
In addition, the plasma CVD device also includes a vacuum exhaust mechanism (not shown) which vacuum-exhausts the inside of the chamber 102. Furthermore, the plasma CVD device also includes a gas supply mechanism (not shown) which supplies a film deposition raw material gas into the chamber (refer to, for example, Patent Literature 1).
In the conventional plasma CVD device described above, since a gap is present between the anode 104 and the anti-adhesion member 91, an abnormal discharge may be generated in the gap while a CVD film is deposited on the substrate to be deposited. When such an abnormal discharge is generated, the formed CVD film may become defective. The generation of an abnormal discharge is required to be suppressed in order that the failure of the CVD film may be reduced.